Scattering pigments are commonly used in coating compositions to achieve opacity in both aqueous systems and non-aqueous systems. Titanium dioxide is commonly used as an opacifying pigment. One limitation in the use of titanium dioxide in aqueous coating compositions is that some of the pigment tends to aggregate. Any aggregation of pigment reduces the efficiency with which it can scatter light. This problem has been minimized in the past by use of surfactants and various dispersion techniques or low cost extenders added to the coating composition to create space between the individual titanium dioxide pigment particles. In other applications, pigment particles have been encapsulated within polymer to create a physical barrier between individual pigment particles and exhibit better dispersion within a polymer system due to the greater compatibility of the polymer enclosed particle than with the polymer system than the pigment particle itself.
More recently, the cost for producing titanium dioxide (TiO2) has increased. Increased cost continues to drive an effort to minimize the amount of titanium dioxide used in coating compositions. One option for extending the amount of TiO2 used in the coating composition is to include TiO2 pigment particles incorporated into hollow particles that also include air voids. These types of particles exhibit enhanced scattering compared to similarly sized TiO2 particles.